Although using SiC wafers as bulk wafers for semiconductor devices such as power devices etc., has attracted attention in recent years, a characteristic of SiC wafers is that they are easily contaminated by impurities and defects such as a crystal defects, etc., often result.
For this reason, in order to improve the performance of semiconductor devices by making a SiC wafer that has high quality and low defect density, an epitaxial film is formed by carrying out epitaxial growth of a SiC single-crystal film on a surface of the SiC wafer, and the result used as an epitaxial wafer.
However, even if an epitaxial film is formed on the surface of a SiC wafer, for some kinds of defects in the SiC wafer, there is a problem that the epitaxial film might have no effect, and the performance of the semiconductor device might be degraded.
In addition to the case of forming the epitaxial film on the SiC wafer, the same problem also might happen in the case of forming the epitaxial film on other types of semiconductor substrates, such as a GaN substrate or a Si substrate.
Accordingly, it will be appreciated that by detecting the crystal defect of the SiC wafer, it may be determined whether the wafer is a suitable wafer on which to form the epitaxial film, and a yield rate may be improved. To that end, it is conceived in Patent Document 1 that by using a so-called cathode luminescence measurement apparatus, the crystal defect of the SiC wafer may be detected.